These projects can be divided into four areas. The headings of these projects are cited below. A. The research on ethyl phosphotriesters of dinucleoside monophosphates and oligonucleotides. 1. Studies on the inhibition of tRNA aminoacylation by deoxyoligonucleoside ethyl phosphotriesters. 2. Hydrogen-bonded complexes of adenine and thymine nucleoside alkyl phosphotriesters in deuteriochloroform. 3. Proton magnetic resonance studies of te conformational changes of dideoxynucleoside ethyl phosphotriesters. B. The research on the structure of short nucleic acid double helices. 1. NMR studies on the structure of complementary deoxytetranucleotides. 2. Proton magnetic resonance (pmr) of short nucleic acid double helices. C. The research on the dinucleoside monophosphate and polynucleotides which have an alkyl substitution in their furanose backbone. 1. Comparative studies on homopolymers of adenylic acid possessing different C2'-substituents of the furanose: d(A) sub n, r(A) sub n, r(2'MeA) sub n, different C2'-substituents of the furanose: d(A) sub n, r(A) sub n, r(2'MeA) sub n, and r(2'EtA) sub n. 2. Conformational study of the two adenylyl-3'-5' (5'-methyl) adenosine diastereomers (rAp(5'-Me)rA's). D. The research on the application of polynucleotide complexes as interferon inducer and inhibitor to viruses. 1. Structural requirements of the rI sub n times rC sub n complex for induction of interferon.